Vaneshi:Intrepid00: Unlike previous versions of Windows Phone before 8 they are upgradeable now since they use the NT kernel.

Not so much. The Windows Phone side of things is still derived and built primarily from CE. Whilst it may have a lot of features similar to it's big brothers it has little to nothing in common with them on a code level.

But you are in all probability correct there will be a Windows Phone 8.1 released around the same time as the service pack for 8 appear but beyond that... not so much.

Ignore their press releases, the marketing bunnies don't know what they're talking about; they used to say each release was a 'total rewrite' until the GDI bug slammed every version of Windows after all.